Radar tracking device



p 1947- D. E. WOOLDRIDGE 2,426,658

RADAR TRACKING DEVICE Filed A 19, 1943 6 Sheets-Sheet '1 FIG. 2

FIG.

FILTER 44 5% ,8

FREQ- colvlr 9 /N l/E N TOR D. E: WOOL DR/D GE A TTORNE V Sgpt. Z, 1947. D. E. WOOLDRIDGE I 2,

RADAR TRACKING DEVICE Filed Aug\ 19, 1943 6 Sheets-Sheet 2 FIG. 4

47 ROLL RECEIVER P/ 7' (H g M07271? T i T 7 /N 5 N TOR 0. 5 WOOL BRIDGE Sept 1947. D. E. WOOLDRIDGE 2,426,658

RADAR TRACKING DEVICE I 42 ROLL t 36 Recs/WA 4/ PITCH Moro/e FIG. 6

4 ROLL MOTOR /N 5 N TOR 0; E mum/06E P 1947. D. E.'WOOLDRIDGE 2,426,658

RADAR TRACKING DEVICE Filed Aug. 19, 1943 6 Sheets-Sheet 4 as 38 FIG-1'7 PITCH Mora/z G) 37 49 0 L are ROLL 2 RECEIVER 0 56 Q 47 .3 4

. Z/Ml/T 07m Pl Tch' RECE/IAE'R 0 INVENTOR D; E WOOLDR/D-GE ATTORNEY p 1947- D. E. WOOLDRIDGE I 2 RADAR TRACKING DEVICE Fi led Aug. 19, 1943 6 Sheets-Sheet 5 F/GQ FIG. /0

FROM RECEIVER FIG. 8

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' lNl/ENTOR 'D. E. WOOLDR/DGE ,4 7'TORNEV Spt. 2, 1947. I D. E. WOOLDRIDGE 2,426,658

RADAR TRACKING DEVICE Filed Aug. 19, 1943 6 Sheets-Sheet e A Z [MU TH TOR INVENTOR D. E WOQLDR/DGE A TTOR/VE y point.

Patented Sept. 2, 194? omrro s'm'rss PAT NT" @FFFECE 2,426,658 r RADAR raacnme DEVICE Dean E. Wooldridge, Chatham, N. J., assignor to Bell Telephone Laboratories, v Incorporated, New York, N. Y., a corporation of New York Application August 19, 1943, Serial No. 499,188

6 Claims.

This invention relates to a method and means for controlling an element responsive to radiated energy.

The object of the invention is to stabilize the element against random movements of the sup- I porting structure, and to control the element so that the element is directed to a desired point.

A feature of the invention is a means for controlling the movement of the element in a horizontal plane in accordance with electrically computed values.

In many distance measuring and object locating systems, it is necessary to direct the energy radiated by some element to some desired point. The energy may be radiated in the form of electromagnetic waves, such as radio, light or heat waves, or of mechanical waves, such as sound waves in air or Water. may be in the form of an antenna, or a reflector of electromagnetic waves, or a transmitter of mechanical waves, such as a microphone, trans- 1 ceiver or low frequency oscillator. may be transmitted by the element and the wave reflected from the desired point received on the 1 same, or another element, or the waves may be 1 radiated from the desired point and received on 1 the element. The element may be mounted on a moving body, such as a marine vessel or aerial '.vehicle which is subject to random movements.

The radiating element The waves ,In accordance with the invention the element ?is supported by a structure stabilized against the :random movements of the moving vehicle, such :as the pitch and roll of a marine vessel or aerial vehicle. The received energy is of such character that the distance from the element to the desired point may be determined. 7 From this determination, electric currents are produced which control motors tilting the element in the vertical plane and rotating the element in the horizontal plane to cause the element to face the desired The invention is disclosed embodied in a system for controlling a radio antenna by waves reflected back from the desired point, but the invention is not limited to this specific use and :may readily be adapted to many other similar systems.

In the drawings:

Fig. 1 shows the geometry relating to the azimuthal angle;

Fig. 2 shows the geometry relating to the tilt angle;

Fig. 3 diagrammatically shows a typical radio system;

Fig. 4 shows a side elevation of the antenna and support;

Fig. 5 shows a view in part section along line 1-1 of Fig. 4;

Fig. 6 shows a detail in part section of the roll drive;

Fig. 7 shows a top view of the support;

' PPI.

Fig. 8 shows a partial sectional view of the support;

Fig. 9 diagrammatically shows a directional gyroscopic control;

Fig. 10 schematically shows the directional rectifier used in Fig. 9;

Fig. 11 shows a summing amplifier for controlling motor relays;

Fig. 12 diagrammatically shows the tilt control motor circuit;

Fig. 13 diagrammatically shows a circuit for indicating the angle (AL); and Fig. 14 diagrammatically shows the azimuth angle control circuit.

For convenience of description, the invention will be described in connection with a system for directing a bomb to fall from an airplane upon a target, but the invention is not limited to this specific use.

In Fig. l the various quantities are shown pro.- jected on the horizontal plane containing the airplane, which, at a given instant, is at the point P and is flying at constant speed and elevation, heading along the course PC. If a wind be blowing, the airplane will be blown off the course, and will actually fl alongsome track, such as If the airplane releases a bomb at the proper instant and continues flying at the same speed along the track, the airplane will reach the point Pi at the instant of impact of the bomb upon the target whose projection is O. The line OP! Will be in the direction of the course PC, and the distance OP! will equal the trail T which is given in the tables for the particular bomb. The projection P0 of the slant distance S from the airplane to the target is commonly known as the horizontal range R. The slant distance S is continuously measured b a radiation responsive device, such as a radio measuring equipment radiating energy from an antenna.

A gyroscopic device maintains an axis PX having a direction fixed in space, and thus indicates the angle L between this axis and the course PC, which is the head to tail axis of the airplane.

The angle A is the azimuth angle between the head to tail axis of the airplane and the horizontal range, and is indicated by the azimuthal rotation of the antenna.

From the angles A and L the angle N may be determined. It will be noted from Fig. 1, that the angle A increases as the airplane approaches the target; The antenna must be controlled to rotate in azimuth with this variation in the angle As the angle N is measured from an axis fixed in direction to the horizontal range, this angle will not be aflected by a change in the course, due to the pilot taking evasive action, as much as the angle A'may be affected and thus is preferred to the angle A, The angle N is equal to Fig. 3. diagrammatically shows a radio transmitter and receiver adapted for use with the present invention. The oscillator I generates a sinusoidal signal current of high stability and a moderate frequency of the order of several thou sand cycles. The current from the oscillator 1 controls th pulse generator 2 which generates one pulse per cycle, of extremely short duration and high amplitude. to the transmitter 3, which maybe a magnetron oscillator. The oscillator 3 generates extremely short pulses of radiant energy which may conveniently have a frequency of several thousand megacycles.

The interval between successive pulses is'suiiiciently long to permit the echo, or reflected pulse, to return from any object within the desired maximum range of the system before the next pulse is transmitted. The signal pulse is transmitted from the transmitter 3 by the'coaxial conductors 4, and the wave guided.

The antenna includes the wave-guide 5and the paraboloidal reflector 6, arrangedso the radiated beam may be rotated in azimuth about a vertical axis and tilted downward from the horizontal to be directed at the target.

The echo reflected from the object-is received by the antenna and conducted by the Wave guide These pulses are supplied ject will be more nearly constant.

5 and coaxial conductor 4 tothe junction with the coaxial conductor 1. Between pulses, the magnetron transmitter '3 presents a very high impedance to the coaxial cable 4 and absorbs very little of the received energy. Substantially all the received energy is transmitted to the transmit-receive switch 8.

The transmit-receive 'sW'itchB may be of any desired type and may conveniently be a Western Electric Company 709A vacuum tube. This vacuum tube is essentially a resonant cavity filled with an ionizable gas. During reception, with the low voltages of the received energy, the gas is not ionized, the cavity-is tuned to resonance and the received energy is conducted'to th frequency converter 9. During the transmission of a pulse, the voltages due to the pulse ionize the gas, thus detuning the cavity and preventing the energy of the pulse from reaching the frequency converter 9 The frequency converter 9 heterodynes the received waves to a convenient intermediate frequency. The intermediate frequency waves are amplified and detected by the amplifier detector Hi and applied'to one of the vertical control plates of a cathode ray tube I I. The received waves cause a sharp upward deflection of the trace ofthe cathode ray beam.

Energy from' the transmitter 3 controls the sweep circuit 12, which, through the push-pull amplifier it connected to the horizontal plates of the cathode ray tube, sweeps the :cathode ray beam across the screen once per pulse.

Current from the oscillator I is selected by'the filter I l and supplied through the adjustable phase shifter'or delay network 15 to the pulse generator 16. Once per pulse, at a definite point in the cycleof the current from the oscillator I the pulse generator H5 produces a voltage which is applied to a vertical plate of the cathode ray tube II and causes the trace of'the cathode ray beam to be abruptly deflected downward, and

retained in the deflected position as =the beam movesfrom left to right. v

The phase shifter =15 may be of the type shown in United States Patent 2,147,728, February 21, 1939, W. T. Wintringham, but, as the phase shift trace-is-moved across the screen of the cathode ray tube.

When the break in the cathode ray trace is moved to coincidence with the deflection due to the received echo, the phase shift or delay in the phase-shifter i5 is made equal to the transit time of the echo or reflected pulse, and is, therefore, a measure of the slant distances from the antenna tothe'reflecting object.

Assuming that the airplane is flying at constant speed and height, the slant distance S from the airplane to the reflecting object will vary rather rapidly, and the rate of change in'the slant distance will also vary. When flying at constant speed, the rate of change in the horizontal distance R from the airplane to the ob- Thus, it is convenient to track the capacitor ,plate I? in terms of the rate of change in horizontal range.

The height, H, horizontal distance, R, and slant distance S are the sides of a right triangle, thus H +R S should equal zero.

A source of voltage 26 is connected across the windings of two potentiometers 2 I, 22. A second source of voltage 23, of opposite polarity to the source 23, is connected across the winding of the potentiometer 24. The windings of potentiometers 21,- 22, 2 3 may conveniently be'in the form or a resistance wire wound smoothly and closely on a thin insulating card, which is supported in a circular arc concentric with the shaft movin the wiper. The width of the cord varies linearly from one end tothe other. The wiper of. potentiometer 2i is'adjusted to select a voltage proportional to 1-1 Current from the source 2-5 is supplied through the phase splitting network formed by the capacitor 2B and resistor 2'5 to one phase winding of the two-phase motor 23.

Current from the source 25 flows through the center tapped inductor 29 to the other phase winding of the motor 28, thence to thewiper of the potentiometer 3e connected across the source .25. .By adjustment of the'wiper 0f potentiometer '30 the speed and direction of rotation of the motor 218 may be controlled. The motor. 28. rotates the wiper of the potentiometer 22 to select a voltage approximately proportional to R The voltages selected by the wipers of the potentio-meters H, 22 24 are supplied to the ampl-ifier 3110f the type shown in Fig. 11. If the sum of the input-voltages is not equal to zero,-the voutput voltage of the amplifier 3i operates :the. motor control relay 32 supplying power from the source '34 and starting the servo-motor 33. The servo-motor 33 rotates the wiper of potentiometer 24' changing the voltage selected by the wiper until the output of the amplifier 35 is reduced-to zero-and the relay "32 is released, and at thesame placement of the wiper of potentiometer 22 proportional to the horizontal distance R.

The resistances per unit length of the windings of potentiometers 2!, 22, 24 increase linearly from beginning to end of the winding, so that if the displacements of the wipers are respectively proportional to H, R, and S, the voltages selected by the wipers will be proportional to H R S Other potentiometer windings may be mounted concentrically with the winding of potentiometer 22, the wipers of these potentiometers also being rotated by the motor 28 proportionally to the horizontal distance R.

The reflector 6 and wave guide 5 may conveniently be supported by the structure shown in Figs. 4 to 8.

In order to insure that the antenna is in a known relationship to the horizontal plane through the airplane, the antenna is supported from a stable element which is not afiected by the pitching and rolling of the airplane.

The base 35 is suspended from some convenient part of the structure of the airplane by bolts passing through holes drilled through the bosses The outer ring 37 is supported by stub shafts 33, 38, Fig. 5, journaled in bearings attached to the outer ring 31 and corresponding bearings in the base 35. The shaft 39, as shown in Fig. 5, extends through the bearing in the base 35 and is geared to a synchronous receiver 40, which may be of the type known commercially as a telegon. The axis of the shafts 38, 39 is preferably normal to the head to tail axis of the airplane.

The pitch control motor M is mounted on the base 35 and geared to a pinion engaging the segmental gear 42 attached to the outer ring 3?.

The pitch control motor 4! is controlled as explained hereinafter to drive the segmental gear 42 so as to maintain the outer ring 3! horizontal even when the airplane pitches. The resultant movement of the outer ring El adjusts the posi tion of the rotor of the receiver 4D with respect to the stator which is attached to the base 35.

The inner ring 33, Fig. 5, is supported by stub shafts journaled in the bearings A l, at attached to the outer ring. The bearings as, as are preferably located on the head to tail axis of the airplane. The stub shaft 6 is extended through the outer ring 3? and geared to a receiver ll of the same type as receiver i-3, mounted on the outer ring 31.

The roll control motor 68 is mounted on a central web of the ring 43, and, as shown in Fig. 6, is connected through gears in gear box 9 with a pinion 5i! meshing with the internal segmental gear 5i attached to the outer ring 3?. The roll control motor 48 is controlled as explained hereinaiter to drive the pinion so over the segmental gear 5! so as to maintain the inner ring 43 horizontal even when the airplane rolls. The resultant movement adjusts the position of the rotor of the receiver ii with respect to the stator. As the pitch and roll adjustments need only cover 29 to degrees of arc, the movement of the inner ring d3 may be limited by suitable stops 52, Fig. 7.

The outer ring 37 and inner ring 43 form a gimbal mounting which permits the motors 4!, ($8 to maintain the web of the inner ring 43 as a stable element which is always horizontal.

The rollers 53, 53, Figs. 5 and 8, are mounted on bolts secured to ears formed on the lower surface of the inner ring 43. A large gear 54 rests upon the rollers 53, 53, and is centered by a shaft 55 iournaled in the web of the ring 43. The shaft 55 is geared to the shaft 56 controlling the wipers of a plurality of concentric potentiometers mounted inside the cover 56.

The azimuth control motor 51, Fig. 7, is mounted on the web of the stable element 43 and geared to a pinion 53 journaled in the stable element and meshing with the large gear 54, Fig. 5. The motor 51 thus can rotate the gear 54 through any desired azimuthal angle.

The antenna support 59, Figs. 4 and 8, is bolted to bosses so, 60 formed in the web of the gear 54. The wave guide 5 is mounted through the refiector 6, which is pivotally attached at mid-point to the antenna support 59.

The tilt control motor 6|, Fig. 4, is bolted to the web of the gear 54 and geared to a segmental gear 62 attached to a crank moving the adjustable rod 63. The rod 63 is pivotally attached to the reflector E at a point below the mid-point of the reflector 6. Operation of the motor ill will tilt the reflector 6 about a horizontal axis. I

Two gyroscopic devices of known type assist in the control of the antenna. The first device, of the artificial horizon type, has a vertically disposed gyroscopic element, and two transmitter elements, which may be arranged to indicate pitching of the airplane from normal on the head to tail axis of the airplane and rolling of the airplane on an axis at right angles to the head to tail axis. The transmitters are essentially small synchronous generators, having the rotors held by the gyroscopic element while the stators are moved by the airplane, and may be of the type known commercially as telegons. The other gyroscopic device is like a gyroscopic compass and maintains an axis PX, Fig. 1, fixed in direction. The transmitter of this device indicates the angle of deviation, L, of the course, or head to tail axis, of the airplane with respect to this axis.

Each of the transmitters of these gyroscopic devices is associated with a control circuit. which may be as shown in Fig. 9. A source of voltage 'lEl excites the transmitter H associated with the gyroscopic device. When the support is displaced with respect to the rotating element of the gyroscope, a voltage is produced by the transmitter ll which is connected to the receiver 12. This voltage is rectified and amplified by the control circuit 13, which may be of the type shown in Figs. 10 and 11, and operates the relay 14.

When the armature of relay 14 is operated upward, current from the power source 69 can flow in the windings of motor 15 turning the motor in one direction. When the armature of relay 74 is operated downward current can flow in the windings of motor 15 turning the motor in the other direction. The relay 14 is continually vibrated by current from the control circuit 13. The shaft of motor 75 is connected to the rotor of the receiver #2, and turns the receiver rotor until the voltage supplied to the control circuit 13 is reduced to zero and the relay l4 alternately supplies equal currents of opposite directions to the winding of motor 15, stopping motor 15. The receiver rotor 12 has thus been turned through the same angle as the transmitter rotor H.

The pitch motor 4| and roll motor 58 both correspond to the motor 15 of Fig. 9 and the pitch receiver 39 and roll receiver 4! correspond to the receiver 12 of Fig. 9.

The voltage from the receiver 12 is supplied to transformer 16, Fig. 10, amplified by vacuum tube H, and the amplified voltage supplied to theinput circuit of vacuum tube 18. The anode circuit of vacuum tube 18: is supplied through resistorv E32;

by vo1tagefromthe-source 70, Fig. 9, which also activates the transmitter. 7 Thus, alternating voltages from-the'source Iii are. appliedito-bot-h' the grid and the anode circuits is positive,-.the anode currentwill be more than.

normal and thervoltage across resistorfiil will be greater than normal.

The voltage source island resistors 85 and-8t are adjusted so as to-cause the direct-current component of the-voltage measured at the junction of 8dand-81= tobe zero when the received alternating current signal is zero. Capacitor 83 isinsertedto filter out-the pulsations. developed across the source 19 and resistor 86 is appliedthrcugh resistor 9 to-thecontrol element of vacuum tube 84. Voltage-from the source 68 is also applied. through resistor, 6'5 tothe control;

from the.- anode of vacuum tube 86 through a source. of alternating current 88- and' a source of voltage 8? to the cathode of vacuum tube 36.

The voltage of the source 81 is adjusted'so that, for normatvoltage applied to the control electrode of vacuum tube 84; the'voltage-across the source 66 and resistor Wis-balanced by the voltage of the source 87 and no: direct current flows in the winding. of relay i l. .Thealternating current from thesource tit-in the winding of relay it causes thev armatures to vibrate, producing equal pulsesof: positive and negative current in the winding ofmotor '75; The motorid is then at rest.

When thereceiver: is unbalanced that-voltageapplied: by resistor 83 through resistorldto the control electrode of'vacuum tube Bil: is larger or smaller: than. normal, and the voltage: applied to the control electrode of vacuum' tube 85 is also larger'or smaller than normal;. The anode-oath ode current-invacuumtube fifi'is correspondingly. changed, upsetting theibalancebetween the voltage acrosssource iifi an-d resistor-55 and the volt.- age of source-8?!, andcausing a direct current to flow in thewinding of rela M This direct current biases the relay M to produce longer pulses of one polarity than the pulses of: the other polarity from the source 69, driving the motor l" in thedirectionto rebalance the receiver 72.

1 The vacuum tube 8 t may conveniently be a double triode, having a cathodecommon to both Similarly, ifthe alternating voltage an The voltage triodes, andacommoncat-hoderesistorflik The:

lower anode is connected, throughsource 90-tothe cathode resistor 89 to stabilize-the. vacuum tube 84= against cathode fluctuations by the method, disclosed in. an article. Sensitive D-G.

Amplifier with AeC Operation, by. S. E. Miller: published in Electronics, November-1941., page27.

Resistors: 9 l 92 are: connected acIOssrtheOiit-Qut. of vacuumtube 8.5; andthejunctionof these ire-- s-istors is connected to the-lower; grid of vacuum; tube 86'. If a negative Voltageis; applied; to-the upper grid of vacuum. tube 84; a positivevoltage.

will be applied to the lower grid of: vacuum-tube-- at. This negative voltage. Will reduce the. currentiii] from source fill-flowing in: resistor 8-9; making the cathode of tube 84 less positive with respectto-the upper grid of vacuum tube 84, which is equivalent to making-this grid lessnegative.

and assists, in theusual manner, iii-controlling.

relay l lso that hunting of motor is:reduced;

In order that the signal may be of maximum, amplitude, the. antenna should bej-tilted, throughv the depression angle E, Fig. 2. In Fig. 2, S sin EH=0. A potentiometer is, mounted'on the support 5 9, Fig. li and the wiper ofthis potentiometer is moved by the tilt-motor 64. The wind-- ing of this potentiometer. has-a" resistancevary ing per unit length.approximatelywith acosinusoidal function sothat i thevoltage selected by the wiper isproportionalto sin- E.. This. potentiometer winding mil; Fig. 12, is connected-acrossa suitable source of voltage NM; The. voltage selected byv the wiperof potentiometer i'illlis: supplied to the winding of a potentiometer N32. The Wiper of potentiometer W2 is driven by motor 33; Fig. 3, proportionally to S to select azvoltage-proportional to S sin E. ihe winding-ofa-potentiorneter E3 is connected across a' source of voltage WA. The Wiper of potentiometer I831 is manually adjusted. to select. a voltage propor tional to H. The amplifier HlEemaybe of the;

type shown in Fig. 11. The voltage selected by the wiper of potentiometer I02, proportional to. S sin E and the voltage selected by the Wiper of. potentiometer IE3, proportional to H. are-supplied to separate input resistors-of amplifier I05, such as the resistors 94, 95,-,Fig. 11.

If the sum of. the voltages supplied to the in:- puts. of amplifier [6.51s not. equalto zero, relay )6 is operated to start motor B l which moves the wiper of potentiometer I00. to makethe. sum of the input voltagesv equal. zero, and, as; shownin Fig. 4 to drive gear 62: and-rod. 63 tilting the antenna 6 through the required angle E.-

The antenna should. have a. pattern of radiation which is highly directive in the horizontal plane so that the azimuthal position of the an-v tennawill accurately determine the angleA, Fig. 1. The antenna, also, should automatically track, or face, the target, or point, 0, even when the airplane turns from the. course PC, and: also as the airplane. approaches the point-0. As the angle- A is measured fromthe course PC to-the hori-- zontal range PO, and the coursePC changeswith" the heading of the airplane,. the antennamay conveniently be controlled by the. angle X.P;,be,- tween the axis; fixed; in direction anditherhorie- Thus, the volt-- age fed back opposes the applied voltage and is-a.

This derivative is portional to AL) .may be of. the typeshownin Fig. 11.

vportionaltoN, in Fig. 13, .a source of voltage IIB issconnected across thewinding of apotentiometer. I I I, insidethe containerjiifi,.Fig.fl8,.and.hav-

ing awipermovedby the shaft .55 and associated gearing, to select .a voltage proportional. to A.

.A source of VoltageHZ of opposite polarityto the source iii) isconnectedacrossthe windings of the .potentiometers M3, lit. .The Wiper of potentiometer H3 is moved bythe servo-motor associatedwith thegyroscopic devicemaintaining the axis PX fixed indirection to .select. atvoltage proportional to +L. The voltage selected bythe Wiper f potentiometer 4 i l isv approximately pro- Thevoltages selected by thewipers of potentiometers Hi, H3, ,lIAare supplied to the amplifierl 5.5, of the type .shown in.Fig..11. The inputs. are connected totheindividual input resistors M, 95, fifiofthe amplifier, Fig. 11. The total input A+L+(AL) should equal zero. If the total input to the amplifier H5 is not equal to zero, relay H8 which isconnected to the output of amplifier H5 will be .operated tostart motor 11?, movingthe wiper of potentiometer.ll iuntilthe total input is equal to zero, relay.II5 is releasedandmotorlll is stopped. The wiper or potentiometer II i will then have. turned through an angle proportional to AL or N. The wipers of other potentiometers ,may be arranged to also be driven by, the shaft of motor iii.

.In Fig. 14, a sourceofvolta'ge i2!) is connected to the winding of potentiometer I2I. The Wiper .of potentiometer I2 Lis moved by motor. I ll, Fig.

13, to select a voltage proportional to A-L, that is, proportional to the angle N, Fig. ,1, which is supplied to the summing amplifier I22, which Iiidesired, thi voltage may be obtained by directly connecting the wiper ofpotentiometer I I4, Fig. 13, to the input of amplifier I22.

A source. of voltage i23is connected across the windingof potentiometer 12a. The voltage selected by the wiper of potentiometer I25 is supplied to the two variable resistors I25, I26 in serial relationship with the source of voltage I27. The sources of voltages I23 and I27 are of the same polarity and the voltage of source I23 is double the voltage of source I21.

The Wiper of potentiometer 524 is moved by the. shaft 56', Fig. 8, proportionally to the angle A, Fig. 1,.between the vertical plane containing the target and the airplane, and the vertical plane through the course, orhead to tail axis of the airplane. The angle Athus may be positive or negative. The voltage of source I 23 is, say, 2V volts, and, assumingthe zero value of A is the mid-point of the winding ofpotentiometer I 24, the voltage selected b the wiper of potentiometer I24 will be ViA volts.

The countervoltagefrom the source I21 is V volts, thus the voltage drop in the resistors I25, I26 will be V A-V, or :A volts. The wiper of variable resistor I25 is moved by motor 28, Fig. 3, to insert a resistance proportional to R, the horizontal distance to the target. The wiper of the variable resistor I25 is adjusted to insert a-resistance proportional to the trail T of the bomb to be used, as given in the tables for this bomb. lhe voltage across the resistor I25 and source I2! is supplied to-the input of thesumming amplifier I22.

The voltage drop proportional to A is thus applied across the resistances proportional to- R+'I', and the voltage- As the, bias ;voltage V is constant,- it maybe used as a comparison voltage in the amplifier, and

-.thus. need; not. ;b econsidered in the balance equa- {honor the a plifie I22- "Voltage from ,t he,source-: I28, ofepposite polarity to the voltages from the sources I20, I23qis applied across the winding of potentiometer I29. The wiper of potentiometer I29 is manually adjustable.

T-he voltages selected by the Wipers of potentiometers I24, 2 I 25 and i29 are-individually supplied tothe inputresistors .94,-:9-5,=- 96-of the summing amplifier of Fig. 11.

The amplifier I22, which is of the type shown in Fig.11, sums up the voltages-irom the wipers ofpotentiometers I2I,-'I29 and-resistor I25, and, if this sum is not zero, relay I 3B'isoperated, starting the azimuth control motor 55'! which movesthe wiper of potentiometer I24 until the sum of the voltages is reduced: to zero, releasing relay I30 and stopping motor -5i. The azimuth control'motor 51, shownin 'Fig. 'I, rotates the antenna through the angle-A.

The voltages suppliedto the summing amplifier I22, will be a voltage proportional to N from the wiper of potentiometer IZI ,-'a voltage proportional to T .v- A

fromthewviper oi resistor i25 and abalance .voltage, -which maybe designated (V+M) from the wiper aof potentiometer i I 29.

Thus, at the balance point where the sum- :of. the inputvolta-ges In-Fig. 1, rAtisthe'angle- OPC,,L isithe angle XPC; thus A-L.lS theangle OPX. .Let the-angle P PX be and=angle OPP]. .be.B. Evidently,

:T iiiT the errorsvinqthegtwo approximations being self- .rc pensatory. hUSn-fOr (.A-L #B-TM.-. 0,;the approximate value may be used.

As the airplane approaches the target area, the bombardier adjusts potentiometer i 29, Fig. 14, causing motor 57 to turn the antenna until the return pulses shown on the cathode ray screen I, Fig. 3, are a maximum. Now, if the airplane changes its course, the angle M will not change, but AL will change in proportion to the angular change of course, thus unbalancing the output of amplifier {122, Fig. 14, and causing motor 51 to continuously turn the antenna to face the target.

As the airplane approaches the target, the angle A continuously increases. This increase produces a proportionate increase in the quantity T R+T again unbalancing the amplifier I22, Fig. 14, and causing motor to continuously turn the antenna to face the target.

What is claimed is:

1. An antenna support including a base, a first ring pivotally supported by saidbase, a first motor mounted on said base and geared to said first ring, a webbed ring pivotally and concentrically supported by said first ring, a second motor mounted on said webbed ring and geared to said first ring, said first and second motors being gyroscopically controlled to maintain said webbed ring horizontal, a plurality of rollers attached to said webbed ring, a shaft centrally journaled in said webbed ring, a gear supported by said rollers and attached to said shaft, a third motor mounted on said webbed ring and driving said gear, an antenna structure supported by said gear, and electrical computing means controlling said third motor to rotate said gear and antenna in azimuth about said shaft.

2. An antenna support including a base, a first ring pivotally supported by said base, a first motor mounted on said base and geared to said first ring, a webbed ring pivotally and concentrically supported by said first ring, a second motor mounted on said webbed ring and geared I, to said first ring, said first and second motors being gyroscopically controlled to maintain said webbed ring horizontal, a plurality of rollers attached to said webbed ring, a shaft centrally journaled in said webbed ring, a gear supported by said rollers and attached to said shaft, a third motor mounted on said Webbed ring and driving said gear, an antenna support mounted on said gear, an antenna motor supported by said gear and geared to said antenna, and electrical computing means controlling said third motor to rotate said antenna in azimuth and said fourth motor to rotate said antenna in elevation.

3. Mechanism for directing to an object the antenna of a dirigible vehicle flying at constant height which includes a base gyroscopically controlled to remain horizontal, a support attached to said base, an antenna pivotally secured to said support, a first motor secured to said base and geared to said antenna, a radio system exciting said antenna, a second motor controlled by indications from said radio system to rotate proportionally to the slant distance from said vehicle to said object, a first voltage source of one polarity, a first potentiometer having a winding connected across said first source, and a first wiper manually adjusted to select a voltage proportional to the constant height of said vehicle, a

second voltage source of opposite polarity, a second potentiometer having a winding connected across said second source and a second wiper moved by said first motor to select a voltage approximately proportional to the sine of the angle of depression from said vehicle to said target, a third potentiometer having a winding connected to said second wiper and a third wiper moved by said second motor proportionally to said slant distance, thermionic means for adding the voltages selected by said first and third Wipers, and means connected to said thermionic means to control said first motor to move said second wiper to reduce the sum of said voltages to zero and to direct said antenna to face said object.

4. The method of tracking a device measuring the azimuth angle of a target with respect to an axis of a bomber airplane which comprises generating a voltage proportional to the magnitude of said azimuth angle multiplied by the ratio of the trail of the bomb to the horizontal range to said target plus the trail of the bomb, and controlling with said voltage the tracking of said device.

5. Mechanism for directing to a target the antenna of a bombing airplane, which includes a base gyroscopically controlled to remain horizontal, an antenna pivotally supported by said base, a first motor geared to said antenna, a radio system exciting said antenna, a second motor controlled by indications from said radio system to rotate proportionally to the horizontal distance from said airplane to said target, a source of a first voltage of one polarity gyroscopically controlled to be equal to the angle between an axis of said airplane and an axis fixed in direction, a second voltage source, a first potentiometer having a winding connected across said second source and a first wiper moved by said first motor, a first variable resistor having a winding connected to said first wiper and a second wiper moved by said second motor, a second variable resistor having a winding connected to said second wiper and a third wiper adjusted to make the resistance of said second resistor proportional to the trail of the bomb, a third voltage source of opposite polarity, a second potentiometer having a winding connected across said third source and a wiper manually adjusted to select a voltage proportional to the angle between said fixed axis and the track of said airplane, thermionic means for adding said first voltage, the voltage across said second resistor and said selected voltage, and means connected to said thermionic means to control said first motor to rotate said antenna and to adjust said first wiper to make the sum of said voltages zero.

6. The method of tracking a device measuring the azimuth angle of a target with respect to an axis of a bomber airplane which comprises establishing a direction fixed in space, generating a first voltage proportional to the angle between said fixed direction and the direction from the airplane to the target, generating a second voltage proportional to said azimuth angle multiplied by'the ratio of the trail of the bomb to the sum of the horizontal range to the target and the trail, generating a third voltage, controlling the tracking of said device with all three of said voltages, and manually varying said third voltage to direct said device to said target.

DEAN E. WOOLDRIDGE. 

